(a) The Field of the Invention
The present invention relates to copolyester compositions having the properties of resisting flame propagation and of being self-extinguishing and thermostable, suitable for the production of flame-resistant formed bodies, in particular textile fibres, and to a process for making the same. Preferably, the copolyester compositions of this invention are essentially based on polyethyleneterephthalate and/or polybutyleneterephthalate.
(b) The Prior Art
Methods for the production of formed bodies, in particular fibres, from copolyesters, that are resistant to flame propagation and/or self-extinguishing, are known in the art. Three techniques are known for imparting to the formed bodies flame-resistance and/or self-extinguishing properties:
(a) the incorporation by extrusion operations of additives which confer such properties, into copolyester compositions;
(b) the use of comonomers which confer such properties in the polymerization;
(c) the application to the previously formed bodies of finishes containing additives which confer such properties.
Techniques (a) and (b) are much preferable to technique (c) for the production of flame-resistant and self-extinguishing copolyester fibres because the application of a finish involves the well known disadvantages that the finish is generally not stable and is progressively removed in the use and washings of the textile articles, and it imparts to the textile articles an inferior hand. Therefore the art is oriented, for the production of self-extinguishing formed bodies, in particular textile articles, to the preparation of essentially polyester compositions which themselves contain one or more self-extinguishing agents.